He was diganosed following a routine medical check up in early August.

The scientist who confessed to leaking nuclear secrets to Libya, Iran and North Korea has been kept under virtual house arrest since 2004.

He is regarded as a national hero by many in Pakistan. President Musharraf pardoned him and denied international investigators access for questioning.

'Best care'

An official statement said further tests on Dr Khan were being conducted by a team of doctors. It did not say how serious his condition is, or if he requires an urgent operation.

"Since the state of health of Dr AQ Khan is of public interest, the government of Pakistan would like to hold out an assurance that the best specialist medical care is being provided to Dr AQ Khan in consultation with his family and personal doctors," the statement from the Ministry of Information said.

"The public will be kept informed from time to time whenever necessary."

Dr Khan has lived in a diplomatic suburb of Islamabad since his televised confession in 2004, in which he admitted nuclear secrets.

Many Pakistanis appreciate his role in developing the country's nuclear arsenal and helping to counter the threat from their nuclear neighbour, India.

The United States and many other countries believe Dr Khan was a rogue nuclear scientist, who used his position to set up an international proliferation network.

President Musharraf denies that Pakistani authorities were ever aware of or involved in Dr Khan's activities, and Pakistani officials say the proliferation network has been completely dismantled.

But a senior US official recently said many questions about the exact nature of the network remained unanswered as there had been no direct access to Dr Khan.